Three-dimensional printing

ABSTRACT

A three-dimensional (3D) object printing kit includes a polymeric material; a fusing agent including at least 5 vol % of a polar solvent; and a detailing agent. The detailing agent includes a non-polar, hydrophobic substance selected from the group consisting of a non-polar, hydrophobic liquid in its liquid state at a temperature ranging from about −80° C. to about 40° C., and a non-polar, hydrophobic wax having a melting temperature less than 120° C.

BACKGROUND

Three-dimensional (3D) printing may be an additive printing process usedto make three-dimensional solid parts from a digital model. 3D printingis often used in rapid product prototyping, mold generation, mold mastergeneration, and short run manufacturing. Some 3D printing techniques areconsidered additive processes because they involve the application ofsuccessive layers of material (which, in some examples, may includebuild material, binder and/or other printing liquid(s), or combinationsthereof). This is unlike traditional machining processes, which oftenrely upon the removal of material to create the final part. Some 3Dprinting methods use chemical binders or adhesives to bind buildmaterials together. Other 3D printing methods involve at least partialcuring, thermal merging/fusing, melting, sintering, etc. of the buildmaterial, and the mechanism for material coalescence may depend upon thetype of build material used.

BRIEF DESCRIPTION OF THE DRAWINGS

Features of examples of the present disclosure will become apparent byreference to the following detailed description and drawings, in whichlike reference numerals correspond to similar, though perhaps notidentical, components. For the sake of brevity, reference numerals orfeatures having a previously described function may or may not bedescribed in connection with other drawings in which they appear.

FIG. 1 is a flow diagram depicting an example of a three-dimensionalprinting method using an example of a detailing agent disclosed herein;

FIGS. 2A through 2D are schematic and partially cross-sectional viewsdepicting the formation of a part layer using an example of a fusingagent and an example of the detailing agent in an example of thethree-dimensional printing method disclosed herein; and

FIG. 3 is a simplified isometric and schematic view of an example of a3D printing system disclosed herein.

DETAILED DESCRIPTION

Disclosed herein are liquid functional agents suitable for use in athree-dimensional printing method that utilizes microwave energy tocoalesce (e.g., melt, fuse, etc.) selected regions of a polymeric buildmaterial layer. As used herein, microwave energy or radiation refers toelectromagnetic radiation with wavelengths ranging from 1 m to 1 mm;with frequencies between 300 MHz and 300 GHz.

One of the liquid functional agents disclosed herein is a fusing agent,which is capable of absorbing microwave radiation and converting theabsorbed radiation to thermal energy which in turn coalesces the buildmaterial that is in contact with the fusing agent. As such, the fusingagent may be used to pattern build material that is to become part of afinal 3D object.

Another of the liquid functional agents disclosed herein is a detailingagent, which is both immiscible with the fusing agent and non-responsiveto the microwave radiation. Its immiscibility with the fusing agentenables the detailing agent to block the fusing agent from spreadinginto undesirable area(s) of a build material layer. Itsnon-responsiveness to microwave radiation keeps the detailing agent fromabsorbing the microwave radiation or otherwise being excited by themicrowave radiation. As such, the build material in contact with thedetailing agent does not heat up and is prevented from coalescing. Thesecharacteristics of the detailing agent help to define the patternedvoxels that are to be coalesced and improve the edge definition of thefinal 3D object.

3D Printing Kits

The polymeric build material, the fusing agent, and the detailing agentdisclosed herein may be part of a 3D printing kit and/or a 3D printingcomposition.

In an example, the three-dimensional (3D) printing kit or compositioncomprises: a polymeric material; a fusing agent including at least 5 vol% of a polar solvent; and a detailing agent, wherein the detailing agentincludes a non-polar, hydrophobic substance selected from the groupconsisting of a non-polar, hydrophobic liquid in its liquid state at atemperature ranging from about −80° C. to about 40° C., and a non-polar,hydrophobic wax having a melting temperature less than 120° C.

In some examples, the 3D printing kit or composition consists of thepolymeric material, the fusing agent, and the detailing agent with noother components. In other examples, the 3D printing kit or compositionmay include other components, such as a coloring agent that is used toimpart color to the final 3D object.

As used herein, “material set” or “kit” may, in some instances, besynonymous with “composition.” Further, “material set” and “kit” areunderstood to be compositions comprising one or more components wherethe different components in the compositions are each contained in oneor more containers, separately or in any combination, prior to andduring printing but these components can be combined together duringprinting. The containers can be any type of a vessel, box, or receptaclemade of any material. In an example, the components of the kit may bemaintained separately until used together in examples of the 3D printingmethod disclosed herein.

Each of the polymeric material, the fusing agent, and the detailingagent utilized in examples of the 3D printing kit will now be described.

Polymeric Material

In the examples disclosed herein, the build material may be anypolymeric material that does not substantially absorb microwaveradiation. The phrase “does not substantially absorb” means that theabsorptivity of the polymeric material at a particular wavelength is 25%or less (e.g., 20% or less, 10% or less, 5% or less, etc.).

Examples of suitable polymeric materials are those that are based onnon-polar monomer segments or low polarity monomer segments such thatthe polymeric materials have low microwave radiation absorptivity. Suchlow microwave radiation absorptivity will be found in polymers made upof molecular segments that have small dipole moment values (i.e., lessthan 0.1 D (debye)) and low mobility. Monomers forming such polymers mayalso have a low dielectric constant (i.e., <<10 and often <5) in theliquid state. The dielectric constant is a dimensionless property of anelectrical insulating material equal to the ratio of the capacitance ofa capacitor filled with the given material to the capacitance of anidentical capacitor in a vacuum without the dielectric material. Somespecific examples of the polymeric material are selected from the groupconsisting of polyethylene, polypropylene, polyvinylidene fluoride(PVDF), polystyrene, acrylonitrile butadiene styrene (ABS),polytetrafluoroethylene (PTFE), thermoplastic synthetic elastomers basedon non-polar monomer segments, and combinations thereof. Some examplesof suitable thermoplastic elastomers are olefinic thermoplasticelastomers which are blends of polyethylene, polypropylene, blockcopolymers of polypropylene, etc. with ethylene propylene rubbers,styrene ethylene butadiene rubbers, etc.

Other polymeric materials may be used, as long as the number of polargroups is low enough to maintain the characteristic that the polymericmaterial does not substantially absorb microwave radiation. For example,some polyamides, polyacetals, polyesters, polyurethanes,polyoxymethylene (POM), polyether ether ketone (PEEK),polyetherketoneketone (PEKK), polyphenylene sulfide (PPS), or copolymersof these materials may be used.

The melting point or melting range or glass transition temperature ofthe polymeric material may depend upon the material used, and in anexample ranges from about 80° C. to about 350° C. For examples,low-density polyethylene materials may melt anywhere from 105° C. toabout 115° C., high-density polyethylene materials may melt anywherefrom 120° C. to about 180° C., polypropylene may melt at about 160° C.,and PTFE may melt around 326° C. It is to be understood that for any ofthe amorphous polymeric materials mentioned herein (e.g., ABS), thematerial has a glass transition temperature.

In some examples, the polymeric material may be in the form of a powder.In other examples, the polymeric material may be in the form of apowder-like material, which includes, for example, short fibers having alength that is greater than its width. In some examples, the powder orpowder-like material may be formed from, or may include, short fibersthat may, for example, have been cut into short lengths from longstrands or threads of material.

The polymeric material may be made up of similarly sized particlesand/or differently sized particles. In an example, the average particlesize of the polymeric material ranges from about 2 μm to about 200 μm.In another example, the average particle size of the polymeric materialranges from about 10 μm to about 110 μm. In still another example, theaverage particle size of the polymeric material ranges from about 20 μmto about 100 μm. The term “average particle size”, as used herein, mayrefer to a number-weighted mean diameter or a volume-weighted meandiameter of a particle distribution. In a specific example, thevolume-weighted mean diameter of a particle distribution of thepolymeric material ranges from about 2 μm to about 200 μm.

In some examples, 100% of the build material is the polymeric material.In other examples, the build material may include the polymericmaterial, along with other additives, such as fillers, whiteners,antioxidants, anti-static agents, flow aids, or combinations thereofthat do not substantially absorb microwave radiation.

Detailing Agent

In examples of the present disclosure, the detailing agent may include anon-polar, hydrophobic substance selected from the group consisting of anon-polar, hydrophobic liquid in its liquid state at a temperatureranging from about −80° C. to about 40° C., and a non-polar, hydrophobicwax having a wax melting temperature less than 120° C.

The non-polar, hydrophobic substance may be present in the detailingagent in an amount ranging from about 80 vol % to 100 vol % of a totalvolume of the detailing agent. In some examples, the non-polar,hydrophobic substance may be present in the detailing agent in an amountranging from about 99 vol % to 100 vol % of a total volume of thedetailing agent.

When the detailing agent includes less than 100 vol % of the non-polar,hydrophobic substance, the detailing agent may also include otheradditives. Suitable detailing agent additives will not substantiallyabsorb microwave radiation and/or will not deleteriously affect thejettability of the detailing agent. As an example of a detailing agentadditive, a dye may be added in an amount of 1 wt % or less. As anotherexample of a detailing agent additive, a second non-polar, hydrophobicsubstance (e.g., a non-polar co-solvent, another non-polar wax, orcombinations thereof) may be used as the balance of the detailing agent.As still another of a suitable detailing agent additive, a non-polarsurfactant may be used.

In some examples of the present disclosure, the non-polar, hydrophobicsubstance is the liquid, and the liquid is an isoparaffinic hydrocarbon.The isoparaffinic hydrocarbon may have any dynamic viscosity suitablefor being selectively applied in accordance with the techniquesdisclosed herein. In some examples of the present disclosure, theisoparaffinic hydrocarbon may have a dynamic viscosity ranging fromabout 0.8 centipoise (cP) to about 40 cP at an application temperatureranging from about −80° C. to about 40° C. Some commercially availableexamples of the isoparaffinic hydrocarbon include those under thetradename ISOPAR®, such as ISOPAR® G (C10-C11 isoparaffin, dynamicviscosity 0.84 cP), ISOPAR® H (C11-C12 isoparaffin, dynamic viscosity1.13 cP), ISOPAR® L (C11-C13 isoparaffin, dynamic viscosity 1.21 cP),ISOPAR® M (C13-C14 isoparaffin, dynamic viscosity 3.04 cP), and ISOPAR®V (dynamic viscosity 13.85 cP) (all of which are available fromExxonMobile).

In other examples, the non-polar, hydrophobic substance is the wax, andthe wax is a paraffin wax, or a polyolefin wax having a melt viscosityof 40 centipoise (cP) or less. The non-polar, hydrophobic wax may form aliquid (sometimes referred to herein as a second liquid) having adynamic viscosity ranging from about 0.8 centipoise (cP) to about 40 cPwhen the non-polar, hydrophobic wax is heated to at least the waxmelting temperature. In these examples, the melted form of the wax isthe non-polar, hydrophobic liquid that can be selectively applied inaccordance with the techniques disclosed herein.

In examples of the present disclosure, the non-polar, hydrophobicsubstance may have a sub-atmospheric distillation temperature lower thana melting temperature or a glass transition of the polymeric material.

The detailing agent may be jettable via piezoelectric inkjet printheadsor thermal inkjet printheads. In some examples, piezoelectric printheadsmay be selected as the jetting efficiency may be enhanced as compared tothermal inkjet printheads.

Fusing Agent

In the examples disclosed herein, the fusing agent includes at least 5vol % of a polar solvent. The polar solvent may make up anywhere from 5vol % to 100 vol % of the fusing agent. The polar solvents are heated astheir component molecules are forced to rotate with the high frequencyelectric field of the applied microwave radiation. In effect, the polarsolvent absorbs the microwave radiation. As such, a higher polar solventcontent may result in higher microwave absorptivity.

Examples of suitable polar solvents include those solvents having adielectric constant greater than 10, and in some instances, greater than20. Some examples include water, formamides, alcohols, ketones, acids,or combinations thereof. Some specific examples includesdimethylformamide, primary aliphatic alcohols, secondary aliphaticalcohols, 1,2-alcohols, 1,3-alcohols, 1,5-alcohols, 2-pyrrolidone,N-methyl-2-pyrrolidone, etc.

In addition to the polar solvent, the fusing agent may also include amicrowave energy absorber. Examples of suitable microwave energyabsorbers or susceptors include carbon black, graphite, various ironoxides (e.g., oxides of iron (II), iron (III), or iron (II, III) (i.e.,magnetite)), or other microwave ferromagnetic nanoparticles.

Examples of suitable carbon black pigments that may be included in thefusing agent include those manufactured by Mitsubishi ChemicalCorporation, Japan (such as, e.g., carbon black No. 2300, No. 900,MCF88, No. 33, No. 40, No. 45, No. 52, MA7, MA8, MA100, and No. 2200B);various carbon black pigments of the RAVEN® series manufactured byColumbian Chemicals Company, Marietta, Ga., (such as, e.g., RAVEN® 5750,RAVEN® 5250, RAVEN® 5000, RAVEN® 3500, RAVEN® 1255, and RAVEN® 700);various carbon black pigments of the REGAL® series, the MOGUL® series,or the MONARCH® series manufactured by Cabot Corporation, Boston, Mass.,(such as, e.g., REGAL® 400R, REGAL® 330R, and REGAL® 660R); and variousblack pigments manufactured by Evonik Degussa Corporation, Parsippany,N.J., (such as, e.g., Color Black FW1, Color Black FW2, Color BlackFW2V, Color Black FW18, Color Black FW200, Color Black S150, Color BlackS160, Color Black S170, PRINTEX® 35, PRINTEX® U, PRINTEX® V, PRINTEX®140U, Special Black 5, Special Black 4A, and Special Black 4).

In some examples of the fusing agent, the carbon black pigment may bedispersed by a polymeric dispersant having a weight average molecularweight ranging from about 12,000 Daltons to about 20,000 Daltons. Inthis example, the fusing agent may include the carbon black pigment, thepolymeric dispersant, and water (with or without a polar co-solvent,such as 2-pyrrolidone). The polymeric dispersant may be any styreneacrylate or any polyurethane having its weight average molecular weightranging from about 12,000 Daltons to about 20,000 Daltons. Somecommercially available examples of the styrene acrylate polymericdispersant are JONCRYL® 671 and JONCRYL® 683 (both available from BASFCorp.). Within the fusing agent, a ratio of the carbon black pigment tothe polymeric dispersant ranges from about 3.0 to about 4.0. In anexample, the ratio of the carbon black pigment to the polymericdispersant is about 3.6. The polymeric dispersant may contribute to thecarbon black pigment exhibiting enhanced electromagnetic radiationabsorption.

The amount of the microwave energy absorber that is present in thefusing agent ranges from 0 wt % to about 40 wt % based on the totalweight of the fusing agent. In other examples, the amount of themicrowave energy absorber in the fusing agent ranges from about 0.3 wt %to 30 wt %, or from about 1 wt % to about 20 wt %. It is believed thatthese microwave energy absorber loadings provide a balance between thefusing having jetting reliability and heat and/or electromagneticradiation absorbance efficiency.

Some examples of the fusing agent may also include surfactant(s) and/ordispersing aid(s), antimicrobial agent(s), anti-kogation agent(s), orother additives that improve the jettability of the fusing agent, theability of the fusing agent to coat the polymeric build material, and/orthe ability of the fusing agent to penetrate into voids among thepolymeric build material.

Surfactant(s) and/or dispersing aid(s) may be used to improve thewetting properties and the jettability of the fusing agent. Examples ofsuitable surfactants and dispersing aids include those that arenon-ionic, cationic, or anionic. Examples of suitablesurfactants/wetting agents include a self-emulsifiable, non-ionicwetting agent based on acetylenic diol chemistry (e.g., SURFYNOL® SEFfrom Evonik, Inc.), a non-ionic fluorosurfactant (e.g., CAPSTONE®fluorosurfactants from DuPont, previously known as ZONYL FSO), andcombinations thereof. In a specific example, the surfactant is anon-ionic, ethoxylated acetylenic diol (e.g., SURFYNOL® 465 from Evonik,Inc.). In other examples, the surfactant is an ethoxylated low-foamwetting agent (e.g., SURFYNOL® 440 or SURFYNOL® CT-111 from Evonik,Inc.) or an ethoxylated wetting agent and molecular defoamer (e.g.,SURFYNOL® 420 from Evonik, Inc.). Still other suitable surfactantsinclude non-ionic wetting agents and molecular defoamers (e.g.,SURFYNOL® 104E from Evonik, Inc.) or secondary alcohol ethoxylates(commercially available as TERGITOL® TMN-6, TERGITOL® 15-S-7, TERGITOL®15-S-9, etc. from The Dow Chemical Co.). Examples of suitable dispersingaid(s) include those of the SILQUEST™ series from Momentive, includingSILQUEST™ A-1230. Whether a single surfactant or dispersing aid is usedor a combination of surfactants and/or dispersing aids is used, thetotal amount of surfactant(s) and/or dispersing aid(s) in the fusingagent may range from about 0.1 wt % to about 6 wt % based on the totalweight of the fusing agent. It is to be understood that thesepercentages may account for the active material in a surfactant(s)and/or dispersing aid(s) that is less than 100% active.

The fusing agent may also include antimicrobial agent(s). Suitableantimicrobial agents include biocides and fungicides. Exampleantimicrobial agents may include the NUOSEPT® (Ashland Inc.), UCARCIDE™or KORDEK™ or ROCIMA™ (Dow Chemical Co.), PROXEL® (Arch Chemicals)series, ACTICIDE® B20 and ACTICIDE® M20 and ACTICIDE® MBL (blends of2-methyl-4-isothiazolin-3-one (MIT), 1,2-benzisothiazolin-3-one (BIT),and Bronopol) (Thor Chemicals), AXIDE™ (Planet Chemical), NIPACIDE™(Clariant), blends of 5-chloro-2-methyl-4-isothiazolin-3-one (CIT orCMIT) and MIT under the tradename KATHON™ (Dow Chemical Co.), andcombinations thereof. In an example, the fusing agent may include atotal amount of antimicrobial agents that ranges from about 0.01 wt % toabout 1 wt %. In an example, the antimicrobial agent is a biocide and ispresent in the fusing agent in an amount of about 0.1 wt % (based on thetotal weight of the fusing agent). These percentages may include bothactive antimicrobial agent and other non-active components present withthe antimicrobial agent.

An anti-kogation agent may also be included in the fusing agent.Kogation refers to the deposit of dried solids on a heating element of athermal inkjet printhead. Anti-kogation agent(s) is/are included toassist in preventing the buildup of kogation, and thus may be includedwhen the fusing agent is to be dispensed using a thermal inkjetprinthead. Examples of suitable anti-kogation agents includeoleth-3-phosphate (commercially available as CRODAFOS™ O3A or CRODAFOS™N-3 acid) or dextran 500 k. Other suitable examples of the anti-kogationagents include CRODAFOS™ HCE (phosphate-ester from Croda Int.),CRODAFOS® N10 (oleth-10-phosphate from Croda Int.), or DISPERSOGEN® LFH(polymeric dispersing agent with aromatic anchoring groups, acid form,anionic, from Clariant), etc. The anti-kogation agent may be present inthe fusing agent in an amount ranging from about 0.1 wt % to about 1 wt% of the total weight of the fusing agent.

The fusing agent may be jettable via any inkjet technology, includingthermal inkjet printheads or piezoelectric inkjet printheads.

3D Printing Method

An example of a 3D printing method using examples of the polymericmaterial, the fusing agent, and the detailing agent disclosed herein isshown in FIG. 1. The method 100 include applying a polymeric material(reference numeral 102); based on a 3D object model, selectivelyapplying a fusing agent on a portion of the polymeric material, whereinthe fusing agent includes at least 5 vol % water (reference numeral104); based on the 3D object model, selectively applying a detailingagent on another portion of the polymeric material, wherein thedetailing agent is a non-polar, hydrophobic liquid that is immisciblewith the fusing agent (reference numeral 106); and exposing thepolymeric material to microwave radiation, whereby the fusing agentincreases in temperature to coalesce the portion of the polymericmaterial in contact with the fusing agent, and wherein the detailingagent is non-responsive to the microwave radiation thereby preventingcoalescence of the other portion of the polymeric material in contactwith the detailing agent (reference numeral 108). This method 100 isalso schematically illustrated in FIGS. 2A through 2C.

As shown in FIG. 2A, some examples of the 3D print method includeapplying a polymeric material 16. The polymeric material 16 may beapplied on a build area platform 12. A printing system (e.g., the system10 shown in FIG. 3) may be used to apply the polymeric material 16. Theprinting system 10 may include a build area platform 12, a buildmaterial supply 14 containing the polymeric material 16, and a buildmaterial distributor 18.

The build area platform 12 receives the polymeric material 16 from thebuild material supply 14. The build area platform 12 may be moved in thedirections as denoted by the arrow 15 (see FIG. 3), e.g., along thez-axis, so that the polymeric material 16 may be delivered to the buildarea platform 12 or to a previously formed layer. In an example, whenthe polymeric material 16 is to be delivered, the build area platform 12may be programmed to advance (e.g., downward) enough so that the buildmaterial distributor 18 can push the polymeric material 16 onto thebuild area platform 12 to form a substantially uniform layer of thepolymeric material 16 thereon. The build area platform 12 may also bereturned to its original position, for example, when a new part is to bebuilt.

The build material supply 14 may be a container, bed, or other surfacethat is to position the polymeric material 16 between the build materialdistributor 18 and the build area platform 12. In some examples, themethod 100 may further include pre-heating the polymeric material 16 inthe build material supply 14 to a supply temperature that is lower thanthe melting temperature or the glass transition of the polymericmaterial 16. As such, the supply temperature may depend, in part, on thepolymeric material 16 used and/or the 3D printer used. In an example,the supply temperature ranges from about 25° C. to about 150° C. Thisrange is one example, and higher or lower temperatures may be used.

The build material distributor 18 may be moved in the directions asdenoted by the arrow 15′ (see FIG. 3), e.g., along the y-axis, over thebuild material supply 14 and across the build area platform 12 to spreadthe layer of the polymeric material 16 over the build area platform 12.The build material distributor 18 may also be returned to a positionadjacent to the build material supply 14 following the spreading of thepolymeric material 16. The build material distributor 18 may be a blade(e.g., a doctor blade), a roller, a combination of a roller and a blade,and/or any other device capable of spreading the polymeric material 16over the build area platform 12. For instance, the build materialdistributor 18 may be a counter-rotating roller. In some examples, thebuild material supply 14 or a portion of the build material supply 14may translate along with the build material distributor 18 such that thepolymeric material 16 is delivered continuously to the materialdistributor 18 rather than being supplied from a single location at theside of the printing system 10 as depicted in FIGS. 2A and 3.

In FIG. 2A, the build material supply 14 may supply the polymericmaterial 16 into a position so that it is ready to be spread onto thebuild area platform 12. The build material distributor 18 may spread thesupplied treated build material composition 16 onto the build areaplatform 12. The controller 62 (FIG. 3) may process “control buildmaterial supply” data, and in response, control the build materialsupply 14 to appropriately position the particles of the polymericmaterial 16, and may process “control spreader” data, and in response,control the build material distributor 18 to spread the polymericmaterial 16 over the build area platform 12 to form the layer ofpolymeric material 16 thereon. As shown in FIG. 2B, one build materiallayer has been formed.

The layer of the polymeric material 16 has a substantially uniformthickness across the build area platform 12. In an example, thepolymeric material layer has a thickness ranging from about 50 μm toabout 120 μm. In another example, the thickness of the polymericmaterial layer ranges from about 30 μm to about 300 μm. It is to beunderstood that thinner or thicker layers may also be used. For example,the thickness of the polymeric material layer may range from about 20 μmto about 500 μm. The layer thickness may be about 2× (i.e., 2 times) theaverage diameter or size of the polymeric material particles, at aminimum, for finer part definition. In some examples, the layerthickness may be about 1.2× the average diameter of the polymericmaterial particles.

As depicted in FIG. 2B, examples of the method 100 include, based on a3D object model, selectively applying a fusing agent 20 on a portion 28of the polymeric material 16. Any example of the fusing agent describedherein may be used, and in an example, the fusing agent 20 may includeat least 5 vol % water. In the portion 28, the fusing agent 20 iscapable of at least partially penetrating into voids between thepolymeric build material particles 16, and is also capable of spreadingonto the exterior surface of the polymeric build material particles 16.

Also as depicted in FIG. 2B, examples of the method 100 further include,selectively applying, based on the 3D object model, a detailing agent 22on another portion 48 of the polymeric material 16. In the other portion48, the detailing agent 22 is capable of at least partially penetratinginto voids between the polymeric build material particles 16, and isalso capable of spreading onto the exterior surface of the polymericbuild material particles 16. The polymeric material 16 and the detailingagent 22 may be applied so that a volumetric ratio of a total volume ofthe polymeric material 16 to a total volume of the applied detailingagent 22 within the other portion(s) 48 ranges from about 2:1 to about200:1.

It is also to be understood that when an agent (e.g., the fusing agent20 or the detailing agent 22) is to be selectively applied to thepolymeric material 16, the agents 20, 22 may be dispensed from anapplicator 24, 24′. The applicator(s) 24, 24′ may each be a thermalinkjet printhead, a piezoelectric printhead, a continuous inkjetprinthead, etc. depending upon the agent 20, 22 that is being dispensed,and thus the selective application of the agent(s) 20, 22 may beaccomplished by thermal inkjet printing, piezoelectric inkjet printing,continuous inkjet printing, etc. The controller 62 may process data, andin response, control the applicator(s) 24, 24′ (e.g., in the directionsindicated by the arrow 15″, see FIG. 3) to deposit the agent(s) 20, 22onto predetermined portion(s) of the polymeric material 16. It is to beunderstood that the agents 20, 22 may be applied in a single printingpass, or may be applied in separate printing passes.

In some examples of the method disclosed herein, the detailing agent 22stored in the applicator 24′ includes the non-polar, hydrophobic liquid,which may be an isoparaffinic hydrocarbon having a dynamic viscosityranging from about 0.8 centipoise (cP) to about 40 cP at an applicationtemperature ranging from about −80° C. to about 40° C. In some theseexamples of the method 100, the selective application of the detailingagent 22 involves ejecting the detailing agent 22 from a piezoelectricprinthead 24′ (see FIG. 2B.)

In some other examples of the method 100, the detailing agent 22 storedin the applicator 24′ includes a non-polar, hydrophobic wax having a waxmelting temperature. In these examples, prior to the selectivelyapplying, the method further includes heating the non-polar, hydrophobicwax to at least its wax melting temperature to form the non-polar,hydrophobic liquid having a dynamic viscosity ranging from about 0.8centipoise (cP) to about 40 cP at the wax melting temperature. Thisconverts the wax form of the detailing agent 22 into a jettable liquidform of the detailing agent 22. Heating of the non-polar, hydrophobicwax may take place in a heating chamber just before it is delivered tothe applicator 24′. Also in these examples, the polymeric material 16may be preheated (for example, by infra-red light) prior to theapplication of the liquid form of the non-polar, hydrophobic wax toprevent the wax from reverting to a solid state when it contacts thepolymeric material 16. It is to be understood that the wax meltingtemperature is below a melting temperature or a glass transition of thepolymeric material 16.

It is to be understood that the other portion(s) 48 that receive thedetailing agent 22 include polymeric material 16 that is not to becomepart of the final 3D object. In some examples, the detailing agent 22may be applied solely at the edges of the patterned portion 28 and/orwherever notches, holes, etc. are to be formed. In these examples, someof the polymeric material 16 (e.g., at the outermost edges of the buildarea platform 12) may not be exposed to the detailing agent 22 or thefusing agent 20. Having non-patterned and non-detailed portions may beused when the polymeric material 16 does not substantially absorb themicrowave radiation on its own. In other examples, the detailing agent22 may be applied to all of the polymeric material 16 that is not tobecome coalesced.

Any example of the detailing agent described herein may be used in themethod 100, and in an example, the detailing agent 22 is a non-polar,hydrophobic liquid that is immiscible with the fusing agent 20. Applyingthe hydrophobic detailing agent 22 adjacent to the edges of thepatterned portion 28 repels the hydrophilic fusing agent 20 in theportion 28, and thus prevents the fusing agent 20 from spreading to theother portion(s) 48, which helps to define the voxels to be coalescedand hence the part form.

After the detailing agent 22 and the fusing agent 20 have been appliedto the respective portions 48, 28, examples of the method 100 includeexposing the polymeric material 16 to microwave radiation 30. Themicrowave radiation 30 may be applied by any suitable microwave heatsource 26, such as microwave point sources or microwave arrays. Somespecific examples include a microwave oven, microwave lamps, a magnetronthat emits microwaves, etc.

The fusing agent 20 is responsive to the microwave radiation. The polarsolvent and any microwave radiation absorber in the fusing agent 20enhance the absorption of the microwave radiation, convert the absorbedradiation to thermal energy, and promote the transfer of the thermalheat to the polymeric material 16 in contact therewith. In an example,the fusing agent 20 sufficiently elevates the temperature of thepolymeric material 16 in the portion(s) 28 to a temperature above themelting point or the glass transition temperature or within the meltingrange of the polymeric material 16, allowing coalescing/fusing (e.g.,thermal merging, melting, binding, etc.) of the polymeric material 16 totake place.

The detailing agent 22 is non-responsive to the microwave radiation 30.As such, the other portion(s) 48 in contact with the detailing agent 22are not heated and do not coalesce. The detailing agent 22 therebyprevents coalescence of the other portion 48 of the polymeric material16.

The application of the microwave radiation forms the object layer 32,shown in FIG. 2C. As shown, the portion 28 of the polymeric material 16patterned with the fusing agent 20 and exposed to microwave radiationbecomes a coalesced block, while the other portion 48 of the polymericmaterial 16 having the detailing agent 22 thereon remains as separableparticles.

In examples of the method 100, the non-polar, hydrophobic liquid of thedetailing agent 22 may have a sub-atmospheric distillation temperaturelower than the melting temperature or the glass transition temperatureof the polymeric material 16. The sub-atmospheric distillationtemperature may be lower than the distillation temperature of thenon-polar, hydrophobic liquid at atmospheric pressure. As such, whenremoval of the detailing agent 22 is desired after printing, the otherportion(s) 48 may be exposed to heating at a suitable sub-atmosphericpressure. For recycling the polymeric material 16 that has not beencoalesced, the method 100 further includes removing the non-polar,hydrophobic liquid from the other portion(s) 48 by heating the otherportion(s) 48 to the sub-atmospheric distillation temperature at acorresponding pressure, thereby causing the non-polar, hydrophobicliquid to evaporate into a vapor. In an example, the other portion(s) 48may be heated to about 100° C. at a pressure of 0.055 atmosphere (atm)to remove at least some of the isoparaffinic hydrocarbons disclosedherein.

The method 100 then includes separating the vapor from the polymericmaterial 16. In an example, the separation of the vapor from thepolymeric material 16 involves pumping the vapor out of a chamber. Insome instances, the recovered polymeric material 16 may be used again ina subsequent print cycle or process.

In examples, the detailing agent 22 may be reclaimed at decaking (wherethe coalesced polymeric material (i.e., printed parts) is removed fromthe powder bed).

At least some of the detailing agent 22 and other solvent(s) (e.g., fromthe fusing agent) that may remain after printing may be removed from theprinted parts and patterned powder bed by vacuum extraction. Vacuumextraction involves heating to the sub-atmospheric distillationtemperature at the corresponding pressure, thereby causing thenon-polar, hydrophobic liquid to evaporate into vapor. Vacuum extractionmay be used prior to decaking, for example, in order to remove at leastsome of the detailing agent 22 from areas adjacent to the printed partsand from the unpatterned powder before the printed parts are removedfrom the powder bed. This extraction process may also remove excessfusing agent solvent(s).

Once the part layer 32 is formed, additional polymeric material 16 maybe applied on the part layer 32, as shown in FIG. 2D. While not shown,it is to be understood that the processes shown in FIGS. 2B and 2C maythen be repeated to form an additional object layer. More specifically,the fusing agent 20 is selectively applied on at least a portion of theadditional polymeric material 16, according to a pattern of across-section for the new layer which is being formed; and the detailingagent 22 is selectively applied on at least another portion of theadditional polymeric material 16 that is not to become part of the newlayer. After the agents 20, 22 are applied, the entire layer of theadditional polymeric material 16 is exposed to microwave radiation inthe manner previously described. The application of the polymericmaterial 16, the selective application of each of the fusing agent 20and the detailing agent 22, and the exposure to microwave radiation 30may be repeated a suitable number of cycles in order to form the final3D object according to a 3D object model.

As such, some examples of the method include iteratively applyingindividual polymeric material 16 layers; based on a 3D object model,selectively applying a fusing agent 20 (including at least 5 vol %water) to at least some portions 28 of at least some of the individualpolymeric material layers to pattern several layers of a 3D object part;based on the 3D object model, selectively applying a detailing agent 22(a non-polar, hydrophobic liquid that is immiscible with the fusingagent 20) to some other portions 48 of the at least some of theindividual polymeric material layers 16; and exposing the individualpolymeric material layers 16 to microwave radiation, whereby any fusingagent 20 present increases in temperature to coalesce respectiveportions in contact with the fusing agent 20 and any detailing agent 22present is non-responsive to the microwave radiation thereby preventingcoalescence of respective other portions in contact with the detailingagent 22. In any given repeated build cycle, it is to be understood thatthe detailing agent 22 may not be applied to the polymeric materiallayer, for example, if the fusing agent 20 is applied to the entirelayer.

3D Printing System

Referring now to FIG. 3, an example of the 3D printing system 10 thatmay be used to perform examples of the method 100 disclosed herein isdepicted. It is to be understood that the 3D printing system 10 mayinclude additional components (some of which are described herein) andthat some of the components described herein may be removed and/ormodified. Furthermore, components of the 3D printing system 10 depictedin FIG. 3 may not be drawn to scale and thus, the 3D printing system 10may have a different size and/or configuration other than as showntherein.

In an example, the three-dimensional (3D) printing system 10, comprises:a supply 14 of build material particles 16; a build material distributor18; a supply of a fusing agent 20 and a supply of a detailing agent 22;applicator(s) 24, 24′ for selectively dispensing the agents 20, 22; acontroller 62; and a non-transitory computer readable medium havingstored thereon computer executable instructions to cause the controller62 to cause the printing system to perform some or all of the methoddisclosed herein.

As mentioned above, the build area platform 12 receives the polymermaterial 16 from the build material supply 14. The build area platform12 may be integrated with the printing system 10 or may be a componentthat is separately insertable into the printing system 10. For example,the build area platform 12 may be a module that is available separatelyfrom the printing system 10. The build area platform 16 that is shown isone example, and could be replaced with another support member, such asa platen, a fabrication/print bed, a glass plate, or another buildsurface.

While not shown, it is to be understood that the build area platform 12may also include built-in heater(s) for achieving and maintaining thetemperature of the environment in which the 3D printing method isperformed.

Also as mentioned above, the build material supply 14 may be acontainer, bed, or other surface that is to position the polymericmaterial 16 between the build material distributor 18 and the build areaplatform 12. In some examples, the build material supply 14 may includea surface upon which the polymeric material 16 may be supplied, forinstance, from a build material source (not shown) located above thebuild material supply 14. Examples of the build material source mayinclude a hopper, an auger conveyer, or the like. Additionally, oralternatively, the build material supply 14 may include a mechanism(e.g., a delivery piston) to provide, e.g., move, the polymeric material16 from a storage location to a position to be spread onto the buildarea platform 12 or onto a previously patterned layer.

As shown in FIG. 3, the printing system 10 also the build materialdistributor 18 and the applicator(s) 24, 24′.

Each of the previously described physical elements may be operativelyconnected to the controller 62 of the printing system 10. The controller62 may process print data that is based on a 3D object model of the 3Dobject/part to be generated. In response to data processing, thecontroller 62 may control the operations of the build area platform 12,the build material supply 14, the build material distributor 18, and theapplicator(s) 24, 24′. As an example, the controller 62 may controlactuators (not shown) to control various operations of the 3D printingsystem 10 components. The controller 60 may be a computing device, asemiconductor-based microprocessor, a central processing unit (CPU), anapplication specific integrated circuit (ASIC), and/or another hardwaredevice. Although not shown, the controller 62 may be connected to the 3Dprinting system 10 components via communication lines.

The controller 62 manipulates and transforms data, which may berepresented as physical (electronic) quantities within the printer'sregisters and memories, in order to control the physical elements tocreate the printed article. As such, the controller 62 is depicted asbeing in communication with a data store 64. The data store 64 mayinclude data pertaining to a 3D object to be printed by the 3D printingsystem 10. The data for the selective delivery of the polymeric material16 and the agents 20, 22 may be derived from a model of the object to beformed. For instance, the data may include the locations on eachpolymeric material layer, etc. that the applicator 24, 24′ is to depositthe fusing agent 20 and/or the detailing agent 22. The data store 64 mayalso include machine readable instructions (stored on a non-transitorycomputer readable medium) that are to cause the controller 62 to controlthe amount of polymeric material 16 that is supplied by the buildmaterial supply 14, the movement of the build area platform 12, themovement of the build material distributor 18, the movement of theapplicators 24, 24′, etc.

As shown in FIG. 3, the printing system 10 also includes the radiationsource 26. Examples of the radiation source 26 include any microwaveradiation source. As shown in FIG. 3, the radiation source 26 may be amodule that is available separately from the printing system 10. Inother examples, the radiation source 26 may be integrated with theprinting system 10.

The radiation source 26 and/or the heater(s) in the build area platform12 may be operatively connected to a driver, an input/output temperaturecontroller, and temperature sensors, which are collectively shown asheating system components 66. The heating system components 66 mayoperate together to control the radiation source 26 and/or the heater(s)in the build area platform 12. The temperature recipe (e.g., heatingexposure rates and times) may be submitted to the input/outputtemperature controller. During heating, the temperature sensors maysense the temperature of the polymeric material 16 on the platform 12,and the temperature measurements may be transmitted to the input/outputtemperature controller. For example, a thermometer associated with theheated area can provide temperature feedback. The input/outputtemperature controller may adjust the radiation source 26 and/or theheater(s) in the build area platform 12 power set points based on anydifference between the recipe and the real-time measurements. Thesepower set points are sent to the drivers, which transmit appropriatevoltages to the radiation source 26 and/or the heater(s) in the buildarea platform 12. This is one example of the heating system components66, and it is to be understood that other heat control systems may beused. For example, the controller 62 may be configured to control theradiation source 26 and/or the heater(s) in the build area platform 16.

It is to be understood that the ranges provided herein include thestated range and any value or sub-range within the stated range, as ifsuch values or sub-ranges were explicitly recited. For example, fromabout 0.8 centipoise (cP) to about 40 cP should be interpreted toinclude not only the explicitly recited limits of from about 0.8centipoise (cP) to about 40 cP, but also to include individual values,such as about 4 cP, 9.8 cP, 13 cP, 45 cP, etc., and sub-ranges, such asfrom about 1 cP to about 14 cP, from about 1.13 cP to about 3.04 cP,from about 1 cP to about 30 cP, etc. Furthermore, when “about” isutilized to describe a value, this is meant to encompass minorvariations (up to +/−10%) from the stated value.

Reference throughout the specification to “one example”, “anotherexample”, “an example”, and so forth, means that a particular element(e.g., feature, structure, and/or characteristic) described inconnection with the example is included in at least one exampledescribed herein, and may or may not be present in other examples. Inaddition, it is to be understood that the described elements for anyexample may be combined in any suitable manner in the various examplesunless the context clearly dictates otherwise.

While several examples have been described in detail, it is to beunderstood that the disclosed examples may be modified. Therefore, theforegoing description is to be considered non-limiting.

What is claimed is:
 1. A three-dimensional (3D) object printing kit,comprising: a polymeric material; a fusing agent including at least 5vol % of a polar solvent; and a detailing agent, wherein the detailingagent includes a non-polar, hydrophobic substance selected from thegroup consisting of a non-polar, hydrophobic liquid in its liquid stateat a temperature ranging from about −80° C. to about 40° C., and anon-polar, hydrophobic wax having a wax melting temperature less than120° C.
 2. The 3D object printing kit as defined in claim 1 wherein thepolymeric material is selected from the group consisting ofpolyethylene, polypropylene, polyvinylidene fluoride (PVDF),polystyrene, acrylonitrile butadiene styrene, polytetrafluoroethylene(PTFE), thermoplastic synthetic elastomers based on non-polar monomersegments, and combinations thereof.
 3. The 3D object printing kit asdefined in claim 1 wherein the non-polar, hydrophobic substance ispresent in the detailing agent in an amount ranging from about 80 vol %to 100 vol % of a total volume of the detailing agent.
 4. The 3D objectprinting kit as defined in claim 3 wherein the non-polar, hydrophobicsubstance is the liquid, and the liquid is an isoparaffinic hydrocarbon.5. The 3D object printing kit as defined in claim 4 wherein theisoparaffinic hydrocarbon has a dynamic viscosity ranging from about 0.8centipoise (cP) to about 40 cP at an application temperature rangingfrom about −80° C. to about 40° C.
 6. The 3D object printing kit asdefined in claim 3 wherein the non-polar, hydrophobic substance is thewax, and the wax is a paraffin wax.
 7. The 3D object printing kit asdefined in claim 6 wherein the non-polar, hydrophobic wax forms a secondliquid having a dynamic viscosity ranging from about 0.8 centipoise (cP)to about 40 cP when the non-polar, hydrophobic wax is heated to at leastthe wax melting temperature.
 8. The 3D object printing kit as defined inclaim 1 wherein the non-polar, hydrophobic substance has asub-atmospheric distillation temperature lower than a meltingtemperature or a glass transition temperature of the polymeric material.9. A three-dimensional (3D) printing method, comprising: applying apolymeric material; based on a 3D object model, selectively applying afusing agent on a portion of the polymeric material, wherein the fusingagent includes at least 5 vol % water; based on the 3D object model,selectively applying a detailing agent on an other portion of thepolymeric material, wherein the detailing agent is a non-polar,hydrophobic liquid that is immiscible with the fusing agent; andexposing the polymeric material to microwave radiation, whereby thefusing agent increases in temperature to coalesce the portion of thepolymeric material in contact with the fusing agent, and wherein thedetailing agent is non-responsive to the microwave radiation therebypreventing coalescence of the other portion of the polymeric material incontact with the detailing agent.
 10. The 3D printing method as definedin claim 9 wherein the non-polar, hydrophobic liquid is an isoparaffinichydrocarbon having a dynamic viscosity ranging from about 0.8 centipoise(cP) to about 40 cP at an application temperature ranging from about−80° C. to about 40° C., and wherein the selective application of thedetailing agent involves ejecting the detailing agent from apiezoelectric printhead.
 11. The 3D printing method as defined in claim9 wherein the non-polar, hydrophobic liquid is a non-polar, hydrophobicwax having a wax melting temperature, and wherein prior to theselectively applying, the method further comprises heating thenon-polar, hydrophobic wax to at least the wax melting temperature toform the non-polar, hydrophobic liquid having a dynamic viscosityranging from about 0.8 centipoise (cP) to about 40 cP at the wax meltingtemperature.
 12. The 3D printing method as defined in claim 9 wherein:the non-polar, hydrophobic liquid has a sub-atmospheric distillationtemperature lower than a melting temperature or a glass transitiontemperature of the polymeric material; and the method further comprises:removing the non-polar, hydrophobic liquid from the other portion byheating the other portion to the sub-atmospheric distillationtemperature at a corresponding pressure, thereby causing the non-polar,hydrophobic liquid to evaporate into a vapor; and separating the vaporfrom the polymeric material.
 13. The 3D printing method as defined inclaim 12 wherein the separating the vapor from the polymeric materialinvolves pumping the vapor out of a chamber.
 14. The 3D printing methodas defined in 9, further comprising applying the polymeric material andthe detailing agent so that a volumetric ratio of a total volume of thepolymeric material to a total volume of the applied detailing agentwithin the other portion ranges from about 2:1 to about 200:1.
 15. Athree-dimensional (3D) printing method, comprising: iteratively applyingindividual polymeric material layers; based on a 3D object model,selectively applying a fusing agent to at least some portions of atleast some of the individual polymeric material layers to patternseveral layers of a 3D object part, wherein the fusing agent includes atleast 5 vol % water; based on the 3D object model, selectively applyinga detailing agent to some other portions of the at least some of theindividual polymeric material layers, wherein the detailing agent is anon-polar, hydrophobic liquid that is immiscible with the fusing agent;and exposing the individual polymeric material layers to microwaveradiation, whereby any fusing agent present increases in temperature tocoalesce respective portions in contact with the fusing agent, andwherein the detailing agent is non-responsive to the microwave radiationthereby preventing coalescence of respective other portions in contactwith the detailing agent.